Regulating device for high frequency power amplifiers



: 1931- J. c. SCHELLENG 7 6,556

REGULATING DEVICE FOR HIGH FREQUENCY POWER A IPLIFIERS ,Filed Nov, 4, 1924 x J glg owzn AMPLIFIERS MM I John Sche/lmg Patented Dec. 15, 1931 UNITED STATES PATENT OFFICE JOHN C. SCHELLENG, OF MILI QBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCOBEORATED, OF NEW YORK, N. Y.,A CORPORATION OF NEW YORK I G DEVICE FOR HIGH FREQUENCY POWER AMPLIFIERS Application filed November 4, 1924. Serial No. 747,799.

This invention relates to amplifying sys-.

terns and more particularly to devices for limiting the output voltage of such systems.

One object of this invention is to prevent the production of an excessive potential in the output circuit of an amplifying system. Another object is to control the energy sup:

' plied to the input circuit of a power amplifier by voltage changes in its output circuit whereby the potential developed in its output circuit is maintained within adesired safe value.

A feature of this invention is a voltage limiting device so connected between the output and input circuits of a power amplifier, that an excessive voltage in' the output circuit reduces the power supplied to the amplifier input circuit.

Novel features which are believed to be characteristic of this invention are pointed outwith particularity in the claims appended hereto. The invention itself, however, both as to the details of its organization and its mode of operation, will be better understood by reference to the following description taken in connection with the accompanying drawing in which the single figure is a diagrammatic representation of a radio signalingzcircuit embodying this invention.

eferring to the drawing, there is shown a modulating system having its output circuit connected by a transformer 2 to the input circuit of a ower amplifier. The first and last stages of the power amplifier are repre sented, by way of example, as space discharge devices 3 and 4 respectively. The modulating system 1 may be of any wellknown type adapted to produce a carrier wave modulated in accordance with signals. Space current is applied to the discharge devices 3 and 4 by sources 5 through inductances 6 which may be either air core inductances or iron core choke coils. These inductances are used to prevent short circuiting the amplified alternating current through the sources 5. Source 21 is ada ted to maintain the grid of repeater 3 at the dbsired negative potential relative to its cathode. The alternating current anode circuit of repeater 4 includes 10 the primary winding of transformer 7, the

'9 is connected across a .from connection 10 for the secondary of. which is connected in theradiating or transmission circuit. Capacity 8 comprising a plurality of units is connected across. the primary winding of the transformer! and cooperates therewith to constitute a circuit tuned to the The voltage limiting device includes the rectifier 9, filter15 and rectifier 19. Rectifier portion of the tuning capacity. One connection 10 is made variableand maybe adjusted to connect one or more of condensers 8 to the rectifier 9 so as to obtain the proper ratio between the voltage roduced in the primary winding of transormer 7 and that supplied to the rectifier 9. Variable condenser 12 is inserted in lead 23 urpose of adusting the coupling between t e power amplifier output circuit and the voltage limiting device. In connection with condenser 14.- it

controls the ratio of voltage applied by condenser 8 to that su plied to coil 13. Inductance 13 acts as a y-pass for direct curent, in the circuit including rectifier 9, around condenser 14. Although rectifier 9 has been shown as a two-element space discharge device having a hot cathode and cold anode, any type of device possessing the property of unilateral conductivity can be used.

The alternating current component of the rectified current flowing through the circuit of I rectifier 9 is prevented from passing through resistance 18 connected in series with rectifier 9 by means of a filter 15. This filter is shown as comprising series inductances 16 and shunt condensers 17. Inductances 16 will offer high impedance to vthe alternating current which will be shunted through condensers 17, while direct current will flow in the circuit including rectifier 9 and inductance 13, inductances 16 and resistance 18. The cathode of rectifier 19 is connected through'battery 20 and resistance 18 to the cathode of the device 3 while its anode is'connected to the grid of device 3 of the power amplifier. Direct current will flow through reslstance 18 such a direction that the terminal of this resistance connectedto the oathode of rectifier 19 will tend to have a negajusting tap 10 tive potential. Rectifier 19, battery 20 and resistance 18 constitute a circuit connected across the grid-cathode circuit of the first power amplifier tube 3 in shunt to the secondary of transformer 2. When the impedance of rectifier 19 is lowered by its cathode becoming negative with respect to its anode, current will flow therethrough so that the potential applied to the grid of device 3 cannot build up beyond a predetermined value.

In the operation of this system the voltage limiting device will be isolated from the input circuit of the first power amplifier tube when the cathode of rectifier 19 is positive with respect to its anode due to the unilateral impedance introduced thereby. When a voltage in excess of a predetermined value is impressed upon the condensers 8 in the output circuit of the power amplifier, current will flow through the rectifier 9 and resistance 18. When the current flowing through the resistance 18 reaches such value that the cathode of rectifier 19 is made negative with respect to its anode the impedance of the rectifying.

device 19 will be reduced, thereby causing the device to act as a load in shunt tothe input or cathode-grid circuit of the first stage 3 of the power amplifier. A certain amount of the input energy supplied by the transformer 2 will be diverted through this shunt ath and hence the control potential impresse upon the grid of the device 3 is prevented from building up. The voltage of battery 20 should be adjusted to a value such that the potential applied to the rectifier 19 due to the voltage drop across the resistance 18 will be sufficient to cause the cathode to become negative with respect to its anode when the voltage in the output circuit of the amplifier across the capacity connected to the rectifier 9 reaches the predetermined value. By adthe limiting or protective device may be set toexercise its control at various voltage levels of the amplifier output.

Although this invention has been shown and described as embodied in a particular circuit, it is understood that it is of general a plication, and hence is not to be limited to t e specific details herein disclosed.

What is claimed is:

1. A space discharge amplifying systemineluding an input circuit for said system "and an output circuit therefor, a circuit interconnecting said input and output circuits includin g a non-conductive impedance comprising means for establishin a conductive ath through said impedance or a portion 0 the input energy when system exceeds a predetermined value.

2. An electrical system comprising an amplifier having wave input and output circuits, a regulating circuit interconnecting said input and output circuits, charge rectifier connected in shunt to said'input circuit and included in said regulating the output voltage of the a space discircuit, and means for controlling the impedance of said rectifier in accordance with the wave voltage in said output circuit where- 'by the input energy of the waves impressed cation of a potential exceeding a certain predetermined value upon the rectifier connected to said output circuit.

4. In an electrical system, an amplifier comprisingspace discharge repeaters having input and output circuits, a voltage limiting device comprising a plurality of rectifiers, means for impressing a voltage derived from said amplifier upon one of said rectifiers, a filter comprising inductance and capacity for preventing alternating currents from passing to said second rectifier, means for applying a voltage to said second rectifier varying in proportion to the voltage impressed upon said first mentioned rectifier, means -for causin said second rectifier to act as a load on sai amplifier when the output potential of said amplifier exceeds a certain predetermined value.

5. A system comprising an electron discharge device amplifier having an input circuit and an output circuit, an auxiliar space discharge device associated with sai input circuit, and means cooperatively associated with the output circuit whereby excessive potential differences across an element of said output; circuit reduce the input energy applied to said amplifier by acting upon the input circuit to establish a conductive path in shunt thereto.

6. In an electrical system, an amplifier comprisingspace discharge devices an input circuit and an output circuit tor said amplifier and a circuit interconnecting said input'circuit and said output circuit, said.

interconnecting circuit including rectifiers and a resistance for preventing the output energy level of said amplifier exceeding a predetermined value.

7. A space discharge amplifying system naaaasa cuit for said amplifier, a variable impedance and means controlled by the output energy of the amplifier to insert said impedance in shunt to said input circuit to control the ratio of the energy supplied to the input circuit with respect to the energy applied to the amplifier. l

9. In an electrical system, a space discharge amplifier, an input circuit cuit for said amplifier, and a circuit interconnecting said input and output circuits including two rectifiers and a resistance which cooperate to control the amplifier.

10. An amplifier having an output circuit and an input circuit, means connected to said output circuit to regulate the energy applied to said input circuit in such manner as to prevent excessive currents in said output circuit and means for rendering said regulatingmeans ineffective to regulate said input energy so long as said output current is less than a predetermined magnitude.

11. An amplifier having an nput circuit and an output circuit and means associated with said output circuit for diverting energy from said input circuit when the magnitude of said output circuit current exceeds a preassigned value, said means remaining ineffective so as to permit said amplifier to operate unaffected by it throughout any range of magnitude of output currents less than said preassigned value.

12. A system comprising a space discharge amplifier having an input circuit, an outputv circuit, a conductive path of variable impedance in shunt to said input circuit and means associated with said output circuit and responsive to potential differences across an element thereof to vary the impedance of said conductive path in accordance with said potential diiferences without, however, in any way affecting said impedance while the output circuit currents lie within any range less than a preassigned limiting ma itude.

13. In combination, an ampli er, an input circuit connected' thereto, an output circuit connected thereto, a pathconnected in shunt across said input circuit having a normal impedance'which is substantially infinite and means operated in response to excess currents in said output circuit to vary the magnitude of said impedance so as to cause it to variably divert energy from said input circuit.

In witness whereof, I hereunto subscribe my name this 3rd day of November A. 1).,

JOHN C. SCHELLENG.

and an output cir- 

